use crate::prelude::{button::update_buttons, *};
use bevy::{input::mouse::*, picking::hover::HoverMap};

pub mod components;
pub mod consts;
pub mod ui;
pub mod utils;

pub struct UiPlugin;

impl Plugin for UiPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Update, scroll_events);
        app.add_observer(on_scroll_handler);

        app.add_systems(Update, update_buttons);
    }
}

fn scroll_events(
    mut mouse_wheel_reader: MessageReader<MouseWheel>,
    hover_map: Res<HoverMap>,
    keyboard_input: Res<ButtonInput<KeyCode>>,
    mut commands: Commands,
) {
    for mouse_wheel in mouse_wheel_reader.read() {
        let mut delta = -Vec2::new(mouse_wheel.x, mouse_wheel.y);

        if mouse_wheel.unit == MouseScrollUnit::Line {
            delta *= LINE_HEIGHT;
        }

        if keyboard_input.any_pressed([KeyCode::ControlLeft, KeyCode::ControlRight]) {
            std::mem::swap(&mut delta.x, &mut delta.y);
        }

        for pointer_map in hover_map.values() {
            for entity in pointer_map.keys().copied() {
                commands.trigger(components::Scroll { entity, delta });
            }
        }
    }
}

fn on_scroll_handler(
    mut scroll: On<components::Scroll>,
    mut query: Query<(&mut ScrollPosition, &Node, &ComputedNode)>,
) {
    let Ok((mut scroll_position, node, computed)) = query.get_mut(scroll.entity) else {
        return;
    };

    let max_offset = (computed.content_size() - computed.size()) * computed.inverse_scale_factor();

    let delta = &mut scroll.delta;
    if node.overflow.x == OverflowAxis::Scroll && delta.x != 0. {
        // Is this node already scrolled all the way in the direction of the scroll?
        let max = if delta.x > 0. {
            scroll_position.x >= max_offset.x
        } else {
            scroll_position.x <= 0.
        };

        if !max {
            scroll_position.x += delta.x;
            // Consume the X portion of the scroll delta.
            delta.x = 0.;
        }
    }

    if node.overflow.y == OverflowAxis::Scroll && delta.y != 0. {
        // Is this node already scrolled all the way in the direction of the scroll?
        let max = if delta.y > 0. {
            scroll_position.y >= max_offset.y
        } else {
            scroll_position.y <= 0.
        };

        if !max {
            scroll_position.y += delta.y;
            // Consume the Y portion of the scroll delta.
            delta.y = 0.;
        }
    }

    // Stop propagating when the delta is fully consumed.
    if *delta == Vec2::ZERO {
        scroll.propagate(false);
    }
}